Wasps legend Lawrence Dallaglio has backed his former side to recover from their woeful season and rediscover their former greatness.

Wasps return to the European arena on Saturday for an Amlin Challenge Cup quarter-final against Biarritz, which should prove a welcome distraction from their Aviva Premiership plight. Although a thrilling victory over Gloucester last weekend eased relegation fears, they are not out of the woods yet, and it remains a possibility that Wasps may have to beat bottom club Newcastle on May 5 to stay up.

It is a different world from the one when Dallaglio's Wasps reigned supreme, winning two European titles and four Premiership crowns between 2003 and 2008. But the former Wasps and England captain is not about to join the disillusioned brigade ahead of Biarritz's arrival at Adams Park.

"Investment is needed at the club, and the club is up for sale at the moment," he said. "I am sure that investment will soon get the agents sniffing back at the door. Trust me, don't worry about that.

"You've only got to see what investment has done to Saracens. It has really turned their position around, and investment at places like Northampton and some of these other clubs, it doesn't take long for things to change. While there are a lot of people being negative about the club, there are a lot of positives around the corner.

"The victory against Gloucester showed that the spirit in the team is still very, very strong, and the signings of James Haskell and Tom Palmer coming back to the club next season show that Wasps can still attract some of the best players, so there are good news stories.

"They are playing in the quarter-final of a European cup this weekend, which bizarrely is something that quite a few other English clubs aren't doing."

There is, though, no escaping a Premiership campaign that has so far produced just six victories from 19 starts and meant prolonged agony for their supporters.

"Everyone at Wasps realises that staying in the Premiership is crucial," added Dallaglio. "If you are in the Premiership then you will still attract players. Obviously, there will have to be a rebuilding process, as there was at Harlequins.

"A couple of years ago, Harlequins were relegated from the Premiership and now they are top of the table. They didn't build themselves up overnight. They did it over a couple of years, and now they are at the top for the first time, which is great for them.

"Wasps have been there, and they know how to get back there. It won't happen overnight. First things first, they have to consolidate this season."

Dallaglio also feels an injury list that has dogged Wasps throughout the season cannot be dismissed lightly.

"I know all clubs have to contend with injuries, but if you look at the scale and the personnel that have been injured these are just not injuries, they are long-term or retirements," he said. "There are the likes of Joe Worsley, Steve Thompson, Tom Rees and Dan Ward-Smith - and that is just this season alone.

"And if you look at last year with Phil Vickery and Raphael Ibanez, it's just one after another, and these are the real leaders in the team. I think what has happened has forced Wasps into rushing some of the younger players with huge potential into first team duty, and it's a really tough thing to do that all at the same time.

"Wasps have just had that experience and real heart ripped out of them in terms of the injuries, so that is probably the biggest factor and one that should not be underestimated when assessing Wasps over the last two years."

Both Wasps and Biarritz have struggled in their domestic competitions, yet Saturday's clash not only has a European semi-final as its prize, but also a home tie later this month against Brive or Scarlets.

"Maybe the welcome distraction of the Amlin Challenge Cup will be good for both sides, and even with Wasps' form today you would still say, at home, they start as favourites," Dallaglio added. "This is the knockout stage of a European cup competition with a trophy at the end of it, so I think regardless of what's happening in the league, this is a game that every club would want to win.

"Wasps are no different from anyone else, and it promises to be an intriguing game."